One conventional form of toothed belt for use with toothed pulleys comprises a rubber belt having an inner toothed portion provided with a cover fabic.
In manufacturing such belts, the cover fabric is placed about a grooved mandrel. A suitable tensile cord is then wrapped about the cover fabric and an outer layer of unvulcanized rubber is wrapped about the tensile cord.
The assembly is then placed in a suitable enclosure and steam introduced thereinto so as to cause fluidization of the unvulcanized rubber. The pressure of the steam urges the rubber inwardly between the turns of the spirally wrapped tensile cord and against the fabric, urging the fabric against the outer surface of the mandrel so as to define an inner cover of the resultant vulcanized toothed belt.
A problem arises in the conventional manufacture of such toothed belts in this manner in that the location of the joint at the end of the fabric may be located at the root of the tooth where substantial wear occurs in the normal use of the belt. Separating of the fabric at that point causes rapid degradation of the belt, such as moisture, oil, etc., and exposes the tensile cords so as to cause early failure thereof.
To avoid such tooth root cracking, the protective fabric cover is arranged on the mandrel so as to attempt to dispose the fabric joint away from the toothed root area. However, it has been found difficult to maintain the location of the fabric joint as the winding of the tensile cord thereabout under substantial tension tends to displace the fabric joint during that operation.